Formatting Data Using Nested Internal Tables

q]] In the following link http://help.sap.com/saphelp_46c/helpdata/en/d3/2e974d35c511d1829f0000e829fbfe/frameset.htm

please find Formatting Data Using Nested Internal Tables

here what does

GET<table name> LATE means?

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q]] Why is it that I need to Refresh WA_SPFLI-SFLIGHT ,& WA_SFLIGHT-SBOOK & Why I do not do the same with WA_SPFLI.